Vinylidene fluoride polymer compositions

ABSTRACT

A resin composition comprising a blend of from about 50 to 99 weight percent of vinylidene fluoride polymer and 1 to 50 weight percent of diallyl phthalate monomer or prepolymer is useful in preparing a coating having high softening point, good heat stability and solvent resistance.

United States atent 1 l3,607,827

[72] Inventors Andrew Anthony Dukert [50] Field of Search 260/41 B,Ambler; 884, 900; I 17/161 UZ Alkis Christoias, Philadelphia, both ofPa. [21 Appl. No. 799,084 [5 6] References Cited [2 Filed Feb. 13, 969UNITED STATES PATENTS [45] Patented Sept. 21,1971 2,377,095 5/1945Muskat 260/784 1 1 Asslgnce Peljnwalt 'P' 3,125,546 3/1964 Pinner eta1... 260/884 ""ladelpma, 3,340,222 9/1967 Fang 260/41 PrimaryExaminer-Allan Lieberman Assistant Examiner-J. H. Derrin ton RIDE PLYMER g [54] o AltorneysCarl A. Hechmer, Jr. and Stanley Litz 10 Claims,No Drawings [52] U.S. Cl 260/41, ABSTRACT: A resin compositioncomprising a blend of from 117/132 CF, 1 17/148, 1 17/161 UZ, 260/41 B,about 50 to 99 weight percent of vinylidene fluoride polymer 260/884,260/900 and 1 to 50 weight percent of diallyl phthalate monomer or [51Int. Cl C08f 45/04, prepolymer is useful in preparing a coating havinghigh soften- C09d 3/76 ing point, good heat stability and solventresistance.

VINYLIDENE FLUORIDE POLYMER COMPOSITIONS The present invention relatesto vinylidene fluoride polymer compositions having improved physical andperformance properties. More particularly, this invention concerns avinylidene fluoride polymer composition containing a modifying amount ofdiallyl phthalate polymer, the mixture being especially useful as acoating for various substrates.

Vinylidene fluoride polymers are recognized and used by the chemicalindustry, construction industries, and related industries ashigh-performance resin coatings. in certain applications, however,polyvinylidene fluoride resin coatings are found to certain solvents, alower than desired softening point, and inadequate heat stability in thepresence of certain pigments. Because of the latter deficiency many ofthe applications for polyvinylidene fluoride which require a whitetitanium dioxide pigment are restricted because discoloration of thecomposition occurs under the relatively rigorous thermal conditions towhich vinylidene fluoride polymers are subjected. This inventionalleviates the foregoing deficiencies by providing a modifiedpolyvinylidene fluoride resin composition having greater heat stability,higher melting point, better solvent resistance and more resistance todiscoloration that the previously known polyvinylidene fluoride resincompositions.

The novel composition of this invention is comprised of a blend of fromabout 50 percent to about 99 percent by weight of vinylidene fluoridepolymer and correspondingly from about 1 percent to 5 percent by weightof diallyl phthalate polymer. The preferred range of the diallylphthalate polymer modifier is from about 1.5 percent to about 12percent, especially in pigment-containing compositions. In anotheraspect of this invention, the composition contains from about 20 toabout 50 parts by weight of TiO pigment per 100 parts by weight of theforegoing combined resins.

A brief but comprehensive survey of polymerization techniques used inpreparing vinylidene fluoride polymers embodied in the composition ofthis invention is found in the specifications of U.S. Pat. No. 2,435,537to Ford et al. and No. 3,193,539 to M. Hauptschein. The terms vinylidenefluoride polymer and polyvinylidene fluoride" used herein refer not onlyto the homopolymer of vinylidene fluoride, but also to the vinylidenefluoride copolymers containing at least about 75 mol percent ofvinylidene fluoride. Suitable comonomers are the halogenated ethylenessuch as sym. dichlorodifluoroethylene, l-chloro-l, 2,2-trifluoroethylene, tetrafluoroethylene, hexafluoropropene, vinylfluoride, vinyl chloride and the like. When at least about 75 molpercent of vinylidene fluoride is present, the important chemicalresistance, resistance to the deteriorative effects of the sun andweather, and mechanical characteristics of the copolymers of vinylidenefluoride are essentially the same as the homopolymer. The primaryparticle sizes of the particulate polyvinylidene fluoride in theformulations herein described are, in general, within the range of about0.05 micron to about l micron in diameter. However, these particles arepresent in the dispersion described below as agglomerates containingfrom one to about 35 primary particles, preferably from one to particlesper agglomerate.

The diallyl phthalate polymer constituting the essential modifying resinembodied in the composition of this invention may be derived fromdiallyl orthophthalate, diallyl isophthalate (metaphthalate), or diallylterephthalate (paraphthalate) monomer, the partially polymerizedprepolymers thereof, or mixtures thereof. The solid prepolymers arelinear, low molecular weight, internally cyclized structures containingunreacted allylic groups spaced at regular intervals along the polymerchains. The prepolymers are prepared by arresting polymerization of theallyl phthalate monomer short of the point where intermolecularcross-linking and gelation occur. (U.S. Pat. No. 3,030,341 to PE.Willard describes the preparation of such prepolymers in detail).

The desired amount of the diallyl phthalate monomer, prepolymer ormixture is admixed with the other components of the coating formulation(i.e., vinylidene fluoride polymer, latent solvent, pigment, etc., thephthalate monomers and triethylphosphate,

prepolymers normally being soluble in the dispersion solvents) togetherwith an effective amount of a free-radical catalyst to catalyze thesubsequent polymerization of the phthalate monomer or prepolymer. Theamount of free-radical catalyst is, in general, from about 1 to about 6percent based on the weight of the diallyl phthalate involved.Representative of operative catalysts are peroxides such as sodium,potassium and ammonium persulfates, caprylyl peroxide, benzoyl peroxide,dicumyl peroxide, pelargonyl peroxide, cumene hydroperoxides, tertiarybutyl diperphthalate, tertiary butyl perbonzoate, sodium peracetate,sodium percarbonate and the like, as well as azobisisobutyronitrile andothers. Preferred, however, are the organic peroxides.

The usual method of utilizing the composition of this invention is toprepare films and coatings on a substrate from a nonaqueous dispersionof polyvinylidene fluoride in an organic latent solvent containing insolution the diallyl phthalate monomer or prepolymer and catalysttherefor, with the pigment, if desired, homogeneously mixed with thedispersion. A latent solvent is defined in the art as an organic liquidhaving a boiling point (at atmospheric pressure) above about 50 C.,preferably about 100-300 C., which liquid has no significant solvent orswelling action on polyvinylidene fluoride at room temperature, but atan elevated temperature exerts a solvent action sufficient to cause thevinylidene fluoride polymer particles to coalesce. Representative latentsolvents include tetraethylurea, dimethyladipate, diethyladipate,diethylsuccinate, dimethylphthalate, diethylphthalate, diethyloxalate,diethylformamide, dimethylsebacate, dimethylsuccinate, propylenecarbonate, ethylene carbonate, gamma butyrolactone, 2-nitropropane,acetone, 4-methoxy-4 methyl pentanone-2, isophorone, methyl ethylketone, cyclohexanone, 2-methoxyethylacetate, 2-butoxyethylacetate,2-ethoxyethylacetate, diethylene glycol monoethyl ether acetate,hexylacetate, diacetone alcohol and others well known in the art. Ingeneral, the quantity of the latent solvent in the polymeric dispersionwill be in the range of from about to about 300 parts by weight perparts by weight of polyvinylidene fluoride. Obviously, the viscosity ofthe polymeric dispersion is decreased as the relative proportion oflatent solvent therein is increased. If desired, other organic volatilediluents which have no latent solvating action on the vinylidenefluoride polymer may be added to reduce the dispersion viscosity, toimprove the flow characteristics, and to promote the wetting action ofthe latent solvent on the polymer powder. The amount of the volatilediluent may be as much as up to about 100 parts per 100 parts by weightof the polyvinylidene fluoride. Examples of such nonsolvent diluents arexylene, toluene, diisobutylketone, aliphatic naphthas, aromaticnaphthas, methyl isobutyl carbinol and others well known in the art.Viscosity of the dispersion can be further reduced by adding from about0.01 to about 2 parts of a cationic surfactant per 100 parts by weightof dispersion solids as disclosed in the application of F. F. Koblitzand R. G. Petrella, S. N. 520,849, filed Jan. 17, 1966, now US. Pat. No.3,441,531, issued Apr. 29, 1969.

The aforesaid dispersions are conveniently prepared by mixing thesubstantially water-free, powdered vinylidene fluoride polymer, latentsolvent, optional volatile solvent, the pigment if needed, the phthalatepolymer precursor and catalyst in a suitable mixing apparatus such as apaint mill, sand mill, ball mill, rodmill, or a high-shear blendingunit. Well-known techniques for laying down the coating compositioninvolve applying the dispersion by spraying or dip coating, or by doctorblade or reverse roll coating to the substrate (e.g., metal, cloth,plastic, wood, glass, etc.). The coated material is inserted in an ovenand dried and cured at from about 250 F. to about 650 F. At theseelevated temperatures final polymerization and curing of the diallylphthalate precursor takes place simultaneously with the fusion andcuring of the matrix vinylidene fluoride polymer to leave a filmcomprised of this durable and compatible resinous mixture.

At the present time the polyvinylidene-fluoride-TiO, dispersionsavailable on the market have incorporated therein a minor amount of anacrylic resin to inhibit discoloration (yellowing) of the coating whenthe films are subjected to high 108 parts of butyrolactone and 300 partsof polyvinylidene fluoride powder.

b. Varying amounts of the catalyzed diallyl phthalate prepolymersolution described in example I (b) are added to curing temperatures. Ithas been found that the compositions 5 separate portions of thepolyvinylidene-fluroride-liO pigof this invention are markedly superiorin their ability to resist ment dispersion (a) and adjusted by addingmethyl isobutyl discoloration while offering the additional advantagesof ketone to give mixtures containing about l2 percent pigment, bettersolvent resistance and increased thermal stability. 28 percent polymerand 60 percent solvent, wherein the con- These advantages areillustrated by the following examples stituencies of the compositionsbased on total resin content which are exemplary only and should not beconstrued as w areasfollows: limitative of the scope of the invention asdescribed and claimed herein. in the examples all ingredients aremeasured RESIN PRQPORTIONS in parts by weight and mixtures are definedby the weight percents of their components.

Vinylidcne EXAMPLE 1 Sample No. Diallyl Phthalate Fluoride PrepolymerPolymer a. 100 parts of polyvinylidene fluoride power (Kynar 501,

a product of Pennsalt Chemicals Corporation) is dispersed n 0% 100% withintensive agitation in a mixture of 80 parts of dimethyl K 15% 985%phthalate and 20 parts of di-isobutyl ketone to give a disper- 2'2: :22:sion comprised of 50 percent polyvinylidene fluoride powder N 225% and50 percent solvents. o 24% 76% b. I00 parts of diallyl orthophthalateprepolymer (Dapon P 35% 65% 35," a product of Food MachineryCorporation) is dissolved o 50% in 120 parts of methyl isobutyl ketone.5 parts of tertiary butyl-perbenzoate catalyst is mixed in.

c. Varying amounts of the foregoing catalyzed diallyl phtha- 406-25 P ofa 40 p solmlo" y f y z late prepolymer solution (b) are added toseparate portions of late'elhlllacrylate P y toluene 'y thepolyvinylidene fluoride dispersion (a) and concentrations Predommemly amelhylmelllacfylale Pf l a Product of are adjusted by the addition ofmethyl isobutyl ketone to give andtllaas Company) ls dlssolved a mixtureof 1,250 polymer-solvent mixtures comprised of about 40 percent Part5 fdlethylene'glycol'monoelhyljelhel' acelafe "f 500 polymer and polymerprecursor, and 60 percent solvents, P dlmelhyl P l 58 P Q2P 8 f Fwherein the constituencies of the compositions based on said 72 Parts ofacryhc Polymer Soluuonmm] resin contemonly are as follo sion are mixed50 parts isophorone, 50 parts butyrolactone and 103 parts of thepreviously described polyvinylidene eval- RESIN PROPORTlONS uated powderto produce a dispersion comprised of 35 percent polymer, l5 percentpigment and 50 percent solvent, wherein the constituency of thecomposition based on total Vmyh en resin content 15 as follows. SampleNo. Diallyl Phthalale Fluoride RESIN PROPORTIONS A 0% most a 2.4% 97.6%5 vinyudcm g Sample No. Acrylic Polymer Fluoride Polymer F, 20% 80% F33.3% 66.7% J 5% 95% o 50% Films (1.2 mils thick) are cast from theforegoing disperf (4 lhl'ck) are cast from the 'f dlspersmns sions Hthrough 0 on aluminum plates and cured at 550 F. for F' chrommlll'pkftedbrass Plates and cured 6 minutes, and the appearance of the films isnoted. The solfmnutes at 400 m an 1 fi'rculaung Oven The melt ventresistance of these pigmented coatings is evaluated by mg appearamfe'and f of t cured m are rubbing a x-inch-thick felt pad soaked indimethyl acetamide f The observanons are Summanzed m the followmg on thesurface of the coating in a reciprocating motion at 2 strokes per secondunder a kilogram load. The results of the attack by this representativesolvent are summarized in the following table: Melting Sample Appearanceof Point. Flexibility sob/cm a C' Resistance A clear 157 good Sam le No.Color of Coating Observations B hazy, r 161 C translucent l 72 good Dhazy, translucent 174 good H intense brownish Coating partially E milkyl93 good discoloration removed after 20 strokes F milky 205 fair .IBrownish discoloration Coating completely G yellowish 2] 0 rglgtbelylnittlq removed after l5 strokes. K Slight trace of yellow Coatingpartially EXAMPLE 2 removed alter 20 strokes; significantly a. 100 partsof 'liO pigment is vigorously dispersed in a lsess [trawl than mixtureof 138 parts of diethylene-glycol-monoethyl-ether l C T i acetate and 46parts of dimethyl phthalate. To this dispersion L No mm 11:12:13; 20

strokes; significantly are added with high-speed stirring 108 parts ofisophorone,

Ta leontinue less removal than Sample H Coating partially removed afterstrokes; significantly less removal than Sample H Coating partiallyremoved in spots after 20 strokes; less removal than M No discolorationN Slight trace of yellow Films (1 mil) are cast side-by-side from theforegoing dispersions onto 1/32 inch aluminum plates. The heat and colorstability of the coatings are determined by exposing the specimens to atemperature of 525 F. in a hot air-circulating oven, withdrawingcomparative samples, and noting the residence time at which failureoccurs as evidenced by discoloration. The results, showing the markedsuperiority of the compositions of this invention, are as follows:

Coating partially removed in spots after 20 strokes; less removal thanSample K.

Very slight surface attack after 20 strokes Very slight surface attackafter 20 strokes O Slight yellowish P Light yellowish Q YellowishEXAMPLE 3 Sample No.

H Dark brown discoloration .l Slight brown discoloration L Nodiscoloration To demonstrate the improved weatherability of thecomposition of this invention, coatings from dispersions identified assample J and sample L are cast on chromate-primed aluminum plates andcured at 550 F. for L5 minutes. The panels are exposed to thedegradative action of a dew cycle weatherometer at 2 cycles/hour for1,000 hours. Sample J panel shows some chalking of the pigment butsample L panel is apparently unaffected by the exposure.

EXAMPLE 4 a. 17.4 parts of TiO (CLNC grade, Titanium Pigment Com pany)is dispersed in a mixture of 12.6 parts diethylene-glycolmonoethyl-etheracetate and 5 parts dimethyl phthalate by grinding in a ball mill.

b. 30.9 parts of polyvinylidene fluoride powder (Kynar 500) is similarlydispersed in a mixture of 15 parts isophorone and 15 partsbutryolactone.

The dispersions (a) and (b) are blended in a high-shear mixer. Weighedamounts of a resin modifier or a precursor resin modifier are thoroughlymixed with portions of the above base dispersion, except for a controlto which no modifier is added. The compositions are as follows:

catalyzed with 3% benzoyl peroxide Sam le No. Stability R Failure in 3minutes S Failure in 5 minutes T Slight discoloration after 5 minutes UTrace of discoloration after 5 minutes W No discoloration after 5minutes What is claimed is:

l. A coated substrate prepared by mixing together a vinylidenc fluoridepolymer, a latent solvent, a component selected from the groupconsisting of diallyl phthalate monomer and prepolymer of diallylphthalate, wherein the proportion of the diallyl phthalate component isfrom about 1 to about 50 percent based on the combined weight of saidcomponent and the vinylidene fluoride polymer, and a freeradicalcatalyst to form a coating composition; coating a substrate with saidcomposition and heating the coating to produce a dried and cured film.

2. A coated substrate according to claim I wherein the coatingcomposition contains from about 20 to about 50 parts by weight oftitanium dioxide per parts by weight of the diallyl phthalate componentand the vinylidene fluoride polymer.

3. A coated substrate according to claim 1 wherein the pro portion ofthe diallyl phthalate component is from about L5 to about 12 percentbased on the combined weight of said component and the vinylidenefluoride polymer.

4. A coated substrate according to claim 3 wherein the coatingcomposition contains from about 20 to about 50 parts by weight oftitanium dioxide per 100 parts by weight of the diallyl phthalatecomponent and the vinylidene fluoride polymer.

5. A coating composition comprised of a dispersion in organic liquidsolvent of vinylidene fluoride polymer and, in solution in said solvent,a component selected from the group consisting of diallyl phthalatemonomer and prepolymers of diallyl phthalate, wherein the proportion ofthe diallyl phthalate component is from about I to about 50 percentbased on the combined weight of said component and the vinylidenefluoride polymer and a free-radical catalyst.

6. A coating composition according to claim 5 having incorporatedtherein from about 20 to about 50 parts by weight of titanium dioxidepigment per 100 parts by weight of the diallyl phthalate component andthe vinylidene fluoride polymer.

7. A composition according to claim 5 wherein the freeradical catalystis present in an amount of about 1 to about 6 percent based on theweight of the diallyl phthalate component.

8. A coating composition according to claim 5 wherein the proportion ofthe diallyl phthalate component is from about 1.5 to about 12 percentbased on the combined weight of said component and the vinylidenefluoride polymer.

9. A composition according to claim 8 having incorporated therein fromabout 20 to about 50 parts by weight of titanium dioxide pigment per 100parts by weight of the vinylidene fluoride polymer and the diallylphthalate component.

10. A composition according to claim 8 wherein the freeradical catalystis present in an amount of about 1 to about 6 percent based on theweight of the diallyl phthalate component.

2. A coated substrate according to claim 1 wherein the coatingcomposition contains from about 20 to about 50 parts by weight oftitanium dioxide per 100 parts by weight of the diallyl phthalatecomponent and the vinylidene fluoride polymer.
 3. A coated substrateaccording to claim 1 wherein the proportion of the diallyl phthalatecomponent is from about 1.5 to about 12 percent based on the combinedweight of said component and the vinylidene fluoride polymer.
 4. Acoated substrate according to claim 3 wherein the coating compositioncontains from about 20 to about 50 parts by weight of titanium dioxideper 100 parts by weight of the diallyl phthalate component and thevinylidene fluoride polymer.
 5. A coating composition comprised of adispersion in organic liquid solvent of vinylidene fluoride polymer and,in solution in said solvent, a component selected from the groupconsisting of diallyl phthalate monomer and prepolymers of diallylphthalate, wherein the proportion of the diallyl phthalate component isfrom about 1 to about 50 percent based on the combined weight of saidcomponent and the vinylidene fluoride polymer and a free-radicalcatalyst.
 6. A coating composition according to claim 5 havingincorporated therein from about 20 to about 50 parts by weight oftitanium dioxide pigment per 100 parts by weight of the diallylphthalate component and the vinylidene fluoride polymer.
 7. Acomposition according to claim 5 wherein the free-radical catalyst ispresent in an amount of about 1 to about 6 percent based on the weightof the diallyl phthalate component.
 8. A coating composition accordingto claim 5 wherein the proportion of the diallyl phthalate component isfrom about 1.5 TO about 12 percent based on the combined weight of saidcomponent and the vinylidene fluoride polymer.
 9. A compositionaccording to claim 8 having incorporated therein from about 20 to about50 parts by weight of titanium dioxide pigment per 100 parts by weightof the vinylidene fluoride polymer and the diallyl phthalate component.10. A composition according to claim 8 wherein the free-radical catalystis present in an amount of about 1 to about 6 percent based on theweight of the diallyl phthalate component.